First two bytes of 'stdout' are lost

[Olivier B.]

Partly answering myself:

For some reason, right after mystdout has been created, i now have to
do mystdout.seek(0) and this solves the issue.

No idea why though..

Le jeu. 11 avr. 2024 à 14:42, Olivier B.
<perso.olivier.barthelemy at gmail.com> a écrit :
>
> I am trying to use StringIO to capture stdout, in code that looks like this:
>
> import sys
> from io import StringIO
> old_stdout = sys.stdout
> sys.stdout = mystdout = StringIO()
> print( "patate")
> mystdout.seek(0)
> sys.stdout = old_stdout
> print(mystdout.read())
>
> Well, it is not exactly like this, since this works properly
>
> This code is actually run from C++ using the C Python API.
> This worked quite well, so the code was right at some point. But now,
> two things changed:
>  - Now using python 3.11.7 instead of 3.7.12
>  - Now using only the python limited C API
>
> And it seems that now, mystdout.read() always misses the first two
> characters that have been written to stdout.
>
> My first ideas was something related to the BOM improperly truncated
> at some point, but i am manipulating UTF-8, so the bom would be 3
> bytes, not 2.
>
> I ruled out wrong C++ code to extract the string from the python
> variable, since running a python print of the content of mystdout in
> the real stdout also misses the two first characters.
>
> Hopefully someone has a clue on what would have changed in Python for
> this to stop working compared to python 3.7?